1. Field of the Invention
The present invention relates to a cement for sealer used for sealing a gap between a gutta-percha point, which is filled in a root canal in a dental root canal treatment, and a root canal wall.
2. Description of the Conventional Art
A root canal treatment is widely carried out. In the root canal treatment, a stable material is filled in a root canal after dental pulp extraction so as to seal a void in the root canal, and thus infection routes between the root canal and periodontal tissue and between the root canal and an oral cavity are blocked. A most widely used method in the root canal treatment includes the steps of filling a thin needle-shaped root canal filler called a gutta-percha point mainly including gutta-percha and zinc oxide in a root canal after dental pulp extraction, and sealing the root canal with a dental cement. At this time, it is necessary to precisely fill the gutta-percha point in the root canal, but the gutta-percha point has insufficient adhesivity to a root canal wall. Thus, in order to increase sealability, a material called a root canal filling sealer is applied on the gutta-percha point, and then the gutta-percha point is filled in the root canal, whereby a gap between the root canal wall and the gutta-percha point is plugged.
As for the root canal filling sealer, a material mainly including zinc oxide and eugenol is widely used. However, the zinc oxide/eugenol-based root canal filling sealer composition can plug the gap between the root canal wall and the gutta-percha point, but has low adhesivity to both the root canal wall and the gutta-percha point. Therefore, there is a problem in sealability to the root canal in a clinical treatment. Further, the eugenol has a toxic action for an organism, and thus there is a problem in safety for a human body.
On the other hand, as for a root canal filling sealer composition using a glass ionomer cement widely used for a dental filling treatment or adhesion, for example, Japanese Patent Application Laid-Open No. 2002-220314 discloses a root canal filling sealer composition including powder for a root canal filling glass ionomer-based sealer, which is made by blending fluoroaluminosilicate glass powder, a polymer not reacting with polycarboxylic acid and/or an inorganic filler not reacting with polycarboxylic acid, and polycarboxylic acid. The root canal filling sealer composition including the powder for a root canal filling glass ionomer-based sealer and the polycarboxylic acid has an object that it can be easily removed from the root canal when the root canal needs to be re-treated.
A dental glass ionomer cement mainly includes a polymer of α-β unsaturated carboxylic acid, oxide powder capable of reacting with the polymer of α-β unsaturated carboxylic acid, and water. Since a sealer composition using the dental glass ionomer cement adheres to both a tooth and a gutta-percha point, the sealer composition has excellent sealability of a root canal, and also is excellent in safety because of having high bioaffinity for a human body. However, the dental glass ionomer cement is set rapidly in general. Thus, in order to use the dental glass ionomer cement for a sealer application, it is necessary to decrease a setting speed so as to secure a sufficient working time. As for a method for decreasing the setting speed, for example, a method by adding a component not reacting with acid and a glass as disclosed in Japanese Patent Application Laid-Open No. 2002-220314, and a method by decreasing the content of acid and/or a glass so as to decrease the amount of ionic bond, can be used. However, when a dental glass ionomer cement is contacted with much water content in a setting process, a metal ion concentration which is a main factor for a setting reaction is decreased, so there is a problem that setting property is decreased. Therefore, when such the root canal filling sealer composition with the prolonged setting speed is used under a condition with much water content such as a dentin in a root canal, setting is hindered and, as a result, there is a problem that a root canal cannot be sealed sufficiently.